Now I know I'll get plenty of flak for this, but I was listening to their latest album last night, so what happened to the Chili Peppers? The Chili Peppers used to be so much fun.

Back in the mid ‘80’s the RHCP was virtually unknown except around local LA and even then they were sort of an oddity. A group of lanky white guys jumping around stage in their underwear playing strong loud (and thanks to Flea) bass driven punky funk..

Flea wailed on the bass, Hillel played the guitar and Anthony couldn't sing (still can't), it was energetic music. It (they) were fun.
Somewhere after “Under the Bridge they changed into writing songs and playing music that they themselves would never have done before, it seems, to appeal to the wider audience they gained after that track came out.
I'd say “sell out” but I know that's not fair…but ask a current fan of RHCP if they like their old stuff (i.e. Freaky Stylely or Uplift Mofo Party Plan or funk music) they don't, and vice versa, their audience has tottally changed. I'd always thought the definition of selling out was changing your music to appeal to a greater audience at the expense of your originality , so…
Its great for a band to evolve, mature and change, and I know they've been through a lot, but the Chili Peppers always had an edge of silliness, fun and spirit, but not anymore.

Yes I know they won a Grammy and all, but Grammies don't really impress me, and their latest album doesn't impress me in the least, kind of anticlimactic considering where they've come from.

Its a long way from the '80's and their music seems average and bland now, a little too introspective and not expressive enough…am I wrong or just refusing to grow up?

Well, "One Hot Minute" was pretty silly at times. But either way, I think they were great until their latest. Their latest is ambitious, but doesn't really deserve to be two discs. It all sounds the same, and it gets boring. They need to shorten some songs, cut out the worst tracks, and put it on one disc.

Stadium Arcadium is still a big hit for them.  I know 'Dani California' and 'Snow (Hey Oh)' were popular